1. Field of the Invention
The present invention relates to a recording medium.
2. Description of the Related Art
An ink jet recording system is a system in which a minute droplet of an ink is applied to a recording medium such as paper by any one of various working principles, and at the same time, a solvent component on the ink penetrates into the recording medium or evaporates, thereby depositing a coloring material component in the ink on the recording medium to make a record of an image, character and/or the like (hereinafter referred to as “image”). In addition, the ink jet recording system has such features that high-speed printability, noise reducing ability and flexibility of a recording pattern are excellent, a multi-color image can be formed with ease, and development and fixing of the image are unnecessary.
In particular, an image formed by a multi-color ink jet recording system can obtain a record comparable with an image formed by multi-color printing of a plate system or a color photography system. Thus, since the system also has such a merit that a printing cost is cheaper than an ordinary printing or photographic technique when the number of images is small, an apparatus of the multi-color ink jet recording system has been rapidly spread as an image recording apparatus of various information instruments in recent years.
A recording medium comparable with a silver salt photograph is required to have excellent color developability, appearance (in particular, scratch resistance) and preservability. A recording medium, or a recording medium having a coloring material receiving layer composed of a porous structure in particular, has many voids. Thus, a recorded image is liable to be faded by an acidic gas in the air, or ozone in particular. Under the circumstances, the recording medium is not suitable for long-term storage of the image compared with the image of the multi-color printing of the place system or the silver salt photograph. The recording medium having the coloring material receiving layer composed of the porous structure is relatively damaged upon conveyance in a printer compared with a swelling type recording medium whose ink receiving layer is composed of a polymer. There has been a very strong demand for improving preservability and scratch resistance, and many proposals for improving such performance properties have been made to date.
Regarding the improvement in preservability, Japanese Patent Application Laid-Open No. 2005-336480 (Patent Literature 1) and Japanese Patent Application Laid-Open No. 2006-265525 (Patent Literature 2) have proposed the use of, for example, a thioether-group-containing cationic polyurethane for improving various properties such as fade resistance. The cationic polyurethane is contained in an ink receiving layer, whereby excellent preservability (in particular, ozone resistance) can be achieved.
In order to improve the scratch resistance on the other hand, Japanese Patent Application Laid-open No. 2006-051741 (Patent Literature 3) describes a recording medium having an ink receiving layer containing a urethane emulsion as a main component and further containing alumina hydrate, polyvinyl alcohol and an organic acid salt of zirconium. Besides the above, Japanese Patent Application Laid-open No. 2006-246017 (Patent Literature 4) describes a recording medium in which two or more ink receiving layers mainly containing silica are provided, and the outermost layer thereof contains a urethane emulsion and a zirconium compound.